1. Field of the Invention
This invention pertains generally to circuit interrupters and, more particularly, to a circuit breaker including a plurality of independent poles which are controlled by a point-on-wave controller.
2. Background Information
Circuit interrupters provide protection for electrical systems from electrical fault conditions such as, for example, current overloads and short circuits. Various circuit interrupters include a spring powered operating mechanism, which opens electrical contacts to interrupt the current through the conductors of an electrical system in response to abnormal conditions, although a wide range of mechanical, electro-mechanical or other suitable driving mechanisms may be employed.
Vacuum circuit interrupters (e.g., vacuum circuit breakers; vacuum reclosers; other vacuum switching devices) include separable contacts disposed within an insulating housing. Vacuum circuit interrupters, such as, for example, power circuit breakers for systems operating above about 1,000 volts, typically utilize vacuum switches (not to be confused with vacuum switching devices), such as vacuum interrupters (not to be confused with vacuum circuit interrupters), as the switch element.
Point-On-Wave (POW) technology is applied to circuit interrupters in order to reduce switching transients (e.g., transient currents; excessive over-voltage) during separable contact closing and to minimize contact erosion during interruption. Such synchronous switchgear is used to reduce the switching transients on equipment and extend the life of the circuit interrupters in, for example, medium and high voltage systems. For example, in a three-pole POW circuit breaker, the three poles are operated independently in order to achieve synchronous or POW switching.
It is known to customize a POW circuit breaker to energize or de-energize one and only one of the following types of loads: (1) a grounded capacitor bank; (2) an un-grounded capacitor bank; (3) a transfer switch (e.g., synchronize the line voltage and the load voltage, in order that they are in the same voltage phase angle when connected to minimize transient currents); (4) a transformer; (5) a medium voltage motor controller; and (6) a shunt reactor (e.g., for grounded high voltage shunt reactors, the three phases should be energized at the maximum value of the phase-to-earth voltage).
When, for example, a capacitor bank, a transfer switch, a transformer or a medium voltage motor controller is switched in, transient over voltages and high compensating currents can occur. To reduce this stress, a customized three-pole POW circuit breaker operates synchronously at specific predetermined phase angles of the line voltages or currents. Such a POW circuit breaker includes three independent operating mechanisms that are controlled differently to achieve the customized POW switching for the specific corresponding load.
Known medium voltage vacuum circuit interrupters employ potential transformers, which have a relatively large size and weight. Such potential transformers are so large and heavy that they must be housed in a separate compartment apart from the corresponding circuit interrupters in the switchgear or motor control center housing.
Known POW circuit interrupters employ customized mechanical parts and/or customized electrical parts in order to create a corresponding set of phase angle switching characteristics for one particular opening and closing application (e.g., for a grounded capacitor bank). In other words, the very same POW circuit interrupter cannot be used to create a different set of phase angle switching characteristics for another different opening and closing application (e.g., for an un-grounded capacitor bank; a transformer; a transfer switch; a medium voltage motor controller).
One known three-pole POW circuit interrupter employs a preprogrammed POW controller that drives three linear actuators to create the corresponding set of phase angle switching characteristics for one particular predetermined opening and closing application. A different POW controller must be used to create a different set of phase angle switching characteristics for another different opening and closing application.
There is room for improvement in circuit interrupters.
There is also room for improvement in circuit breakers including plural independent poles.